Download Current Electricity Introduction

Electricity?
• Electricity is all about electrons, which are the
fundamental cause of electricity
• Static Electricity - involves electrons that are
moved from one place to another, usually by
rubbing or brushing
• Current Electricity - involves the flow of electrons
in a conductor
Electric Charge
• Two kinds: positive and negative (terms coined by
Benjamin Franklin)
• When you rub a glass rod with silk, the charge that
is left on the glass was called positive. If you rub a
hard rubber rod with silk, the charge left on the
rod was called negative.
• Like charges repel while unlike charges attract.
Atoms Are Everywhere
 Electrons move in and out of fixed pathways around the
nucleus
 Changing the number of electrons in a particular type of
atom creates an ion of that atom
Current = Conduction
 Movement of free electrons creates an electric
current
 Materials with large numbers of free electrons are
called electrical conductors. They conduct electrical
current.
 Movement of the electrons physically from one place
to another is slow. Transfer of the energy from one
electron to another happens fast.
Conductors
and
Insulators
• CONDUCTORS - are materials that allow electric charges to
move freely on or through them.
Example – metals (ie. copper), salt solutions,
*These materials do not hold static charges, since
electrons move around
• INSULATORS - are materials that do NOT allow electric charges
to move freely on or through them.
Examples – rubber, glass, plastic
*These are the materials may hold static charges, since
electrons stay in one spot.
Semi-Conductors
• SEMI-CONDUCTORS or RESISTORS- are materials that may allow
electrons to move, but to varying degrees (in-between conductors or
insulators).
• Conductivity testers can be used to test how well electricity can flow. A
conductivity tester contains a battery, an LED light and 2 leads or
electrodes.
• If an object is a good conductor, it will cause the LED to blink rapidly or
light up continuously when touching the electrodes.
• If an object is an insulator, the LED will not glow at all.
• If an object is a semi-conductor, the LED will blink, but slowly.
Simple Circuits
• Don’t let the name fool you
• Bottom line: For electric current to flow,
there has to be a complete pathway for
it…a complete circuit.
Closed and Open Circuits
 Closed Circuit - an unbroken path of conductors
through which electric current flows
 Open Circuit - a circuit with a break in the
conductive path, so no current flows
Know Your Symbols
 Battery or Power Supply
 Resistor
 Capacitor
 Switch
 Conductive Wire
Series Circuits
 An electrical circuit with only one path for
the electrical current to follow
Parallel Circuits
 An electrical circuit that provides more than one
path for the electrical current to follow.